DNA Repair Perspectives in Thyroid and Breast Cancer: The Role of DNA Repair Polymorphisms

One of the great challenges of modern molecular biology is the integration of new genetic information into procedures that can be implemented in rapid, cost effective and reliable methods to genotype, phenotype, identify gene function, and development treatment for the disease. One of the major impacts of such methods and procedures is the increase of our knowledge and understanding of human biology leading to the recognition of the importance of molecular factors in disease aetiology. The immediate consequence of such knowledge is an increased ability for pathology diagnostic and for the identification of presymptomatic individuals or those susceptible to specific diseases, improving our ability for disease prognosis and to develop more efficient therapeutic strategies. Every organism is exposed to hazardous agents in its environment on a continual basis. As a result, organisms have evolved sophisticated pathways that are considered an environmental response machinery, to minimize the biological consequences of hazardous environmental agents. A large number of human genes, including the ones involved in the environmental response machinery, are subject to genetic variability, which can be associated with the altered efficiency of a biological pathway (Perera & Weinstein, 2000). So, an individual’s risk for developing a disease stemming from an environmental exposure might be dependent on the efficiency of his/her own unique set of environmental response genes. These genes are usually involved in the metabolism of environmental carcinogens, in the repair of DNA lesions induced by exogenous and endogenous carcinogens, and in the control of the cell cycle. Individual polymorphic forms in those genes have been associated with individual susceptibility to different types of cancer namely in breast and thyroid cancer (Conde et al., 2009; Gaspar et al., 2004; Pabalan et al., 2010; Peng et al., 2011; Silva et al., 2005; Silva et al., 2006b; Silva et al., 2006a; Silva et al., 2009; Silva et al., 2010; Silva et al., 2007). Several enzymes have evolved for the detoxification of xenobiotic compounds, and their gene expression is induced in response to the presence of numerous compounds (e.g., polycyclic aromatic hydrocarbons found in tobacco smoke). An inefficient detoxification of reactive endogenous or exogenous compounds ultimately leads to lesions in DNA, which should be repaired by DNA repair mechanisms, ought to reduce cancer risk. As a